Abstract
Breakdown phenomena are investigated at continuous isothermal (20∘C) and galvanostatic (0.2–5 mA cm−2) anodizing of aluminum in ammonium salicylate in dimethylformamide (1 M AS/DMF) electrolyte. From the kinetic -curves, the breakdown voltage () values are estimated, as well as the frequency and amplitude of oscillations of formation voltage () at different current densities. The surface of the aluminum specimens was studied using atomic force microscopy (AFM). Data on topography and surface roughness parameters of the electrode after electric breakdowns are obtained as a function of anodization time. The electrode surface of anodic films, formed with different current densities until the same charge density has passed (2.5 C cm−2), was assessed. Results are discussed on the basis of perceptions of avalanche mechanism of the breakdown phenomena, due to the injection of electrons and their multiplication in the volume of the film.
Highlights
Breakdown voltages are an important feature of the process of formation of anodic oxide films on valve metals
Breakdowns are typically recorded in galvanostatic-isothermal regimes, where the formation voltage (U f ) increases linearly with time (t), respectively, with the charge density passed (Q f ) until the “first spark voltage” (UFS) is reached
Breakdown phenomena in barrier anodizing can reasonably be interpreted by models, predicting avalanche mechanism [3,4,5]
Summary
Breakdown voltages are an important feature of the process of formation of anodic oxide films on valve metals. Breakdown phenomena in the formation of barrier anodic films are most successfully interpreted by the models [3,4,5] of an avalanche mechanism. According to these models breakdowns are a result of injection of electrons from the electrolyte [6] in the anodic film and their multiplication during growth of the film [3]. It is of certain interest to study changes in the electrode surface as a result of breakdowns, occurred during anodization at different current densities
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